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assigning WinProc problem.

Started by Jason2Jason Jan 24, 2003 at 6:54 PM 6 replies 200+ views

Original Post

Jan 24, 2003 at 6:54 PM

Hey ppl. I got a unusual compiler problem today, saying that it cant convert the WinProc function to a type. Heres the compiler error:

error C2440: '=' : cannot convert from 'long (__stdcall CWindow::*)(struct HWND__ *,unsigned int,unsigned int,long)' to 'long (__stdcall *)(struct 
HWND__ *,unsigned int,unsigned int,long)'
        There is no context in which this conversion is possible

Here is there winproc definition and the part where i assign it:

    
LRESULT CALLBACK WndProc(	HWND	hWnd,					// Handle For This Window

							UINT	uMsg,								// Message For This Window

							WPARAM	wParam,								// Additional Message Information

							LPARAM	lParam)								// Additional Message Information



	//Registering the Window Class

    //WndClass.cbSize        = sizeof(WNDCLASSEX);

    //WndClass.style         = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;

    WndClass.lpfnWndProc   = WndProc;
    //WndClass.cbClsExtra    = 0;

    //WndClass.cbWndExtra    = 0;

    //WndClass.hInstance     = *hInstance;

    //WndClass.hIcon         = LoadIcon(NULL, IDI_APPLICATION);

    //WndClass.hCursor       = LoadCursor(NULL, IDC_ARROW);

    //WndClass.hbrBackground = NULL;

    //WndClass.lpszMenuName  = NULL;

    //WndClass.lpszClassName = ClassName;

    //WndClass.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);


//Comments above are to show you the ones i'm not talking about to point out the line that i am.

Extra info: I tried to use a typecaste "(WinProc)" as i saw in other apps, but this didnt work. Also the winproc function and the setup code is part of a window C++ class. Any idea how to solve this problem? -J [edited by - jason2jason on January 24, 2003 8:02:38 PM]

Jason2Jason

Jan 24, 2003 at 8:01 PM

No, it made another error saying: 1 unresolved externals.

hmm,

-J

boohillie

Jan 24, 2003 at 10:47 PM

Whoops I wrote the definition wrong.
try this:
static LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

I had WPARAM and LPARAM switched. My bad.

I tried it just now and it works, here''s my code.

  
#include <windows.h>

class CWindow
{
   public:
      CWindow(char*, int, int);

   private:
      WNDCLASSEX  wc;
      HWND        hWnd;
      static LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
};

CWindow::CWindow(char* title, int width, int height)
{
   HINSTANCE hInstance = GetModuleHandle(NULL);

   wc.cbSize = sizeof(WNDCLASSEX);
   wc.style = 0;
   wc.lpfnWndProc = WndProc;
   wc.cbClsExtra = 0;
   wc.cbWndExtra = 0;
   wc.hInstance = hInstance;
   wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
   wc.hCursor = LoadCursor(NULL, IDC_ARROW);
   wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
   wc.lpszMenuName = NULL;
   wc.lpszClassName = TESTWINDOW;
   wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

   RegisterClassEx(&wc);

  hWnd = CreateWindowEx(
      WS_EX_CLIENTEDGE,
      title,
      title,
      WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, CW_USEDEFAULT, width, height,
      NULL, NULL, hInstance, NULL);

  ShowWindow(hWnd, SW_SHOW);
  UpdateWindow(hWnd);

}

LRESULT CALLBACK CWindow::WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
   switch(msg)
   {
      case WM_CLOSE:
         DestroyWindow(hWnd);
         break;
      case WM_DESTROY:
         PostQuitMessage(0);
         break;
      default:
         return DefWindowProc(hWnd, msg, wParam, lParam);
   }

   return 0;
}

      


INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
   MSG msg;
   CWindow win("Test", 640, 480);

   while(GetMessage(&msg, NULL, 0, 0))
   {
      TranslateMessage(&msg);
      DispatchMessage(&msg);
   }

   return msg.wParam;
}

DerekSaw

Jan 24, 2003 at 10:51 PM

Hopes you know what the static keyword mean.

Jason2Jason

Jan 25, 2003 at 6:34 AM

First of all, i put the static keyword infront of the existing definition, so if you got the first one wrong, it woulnd''t have mattered.

Secondly, i do know what it means. I wasn''t sure if it could be used for functions or not so i tried anyway. It means that the variable will still exist even if it goes out of scope.

So, are there any other idea of how i could be going wrong?

Thx,

-J

Jason2Jason

Jan 25, 2003 at 8:36 AM

Well right now i think i''ll only need one CWindow in the game.. i might just creat the winproc out side the class, and pass a pointer from that, to the class.. This would make my class more reusable than it presently is..

Thanks for all the help..

-J

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